Various industrial applications require structural materials which are capable of extended use at high temperatures (above 600.degree. F.) and have high specific strength, that is high strength-to-weight ratios. One class of such materials is honeycomb. These structures can be compositionally and geometrically tailored to exhibit controlled mechanical, electrical and chemical properties useful in the commercial sector, such as high powered dielectric lenses, filter media, microwave absorbers and small, lightweight electrical heating elements.
Previous attempts to fabricate honeycomb and composites from organic polymer materials suffer from the inability to use the resultant materials at high temperatures. Attempts to use refractory fibers and pre-ceramic polymer-derived ceramic materials in laminated composite form have resulted in compositions of relatively high density and therefore low specific strength. Ceramic foams, which have also been used for these purposes, suffer from low specific strength and do not always allow cooling of the ceramic foam body, especially in deep sections. Applications of these materials as filter media are limited by the large occluded volume they occupy. Most prior art attempts to produce tailored electrical properties have been insufficient because of limitations on geometric placement of the electrically active (e.g., ohmic loss elements) materials within the ceramic body.